Normal thyroid tissue has a strong ability to selectively uptake or concentrate iodine. When thyroid nodules are detected, thyroid static planar imaging is required to determine the nature of the nodules. A cool thyroid nodule refers to a nodule where the radioactivity is reduced compared to the surrounding normal thyroid tissue or where there is no radioactive concentration, respectively called cool nodules and cold nodules, indicating hypofunctional or non-functional nodules. Pathologically, malignant lesions account for about 20.3% of cool and cold nodules, followed by benign degenerative lesions such as thyroid cysts, cystic degeneration of adenomas, hemorrhage, or calcification. Some believe that benign cold nodules have clear edges, regular shapes, and no destruction of thyroid tissue. In contrast, cancerous nodules have unclear edges, irregular contours, and distorted thyroid morphology due to tissue destruction, but a definitive diagnosis requires pathological examination.